This invention relates to an intake manifold of an internal combustion engine.
Internal combustion engines generally include intake manifolds adapted for distributing intake air introduced thereinto through a throttle valve within a throttle body, into engine cylinders. The intake manifolds have a hole for introducing canister purge gas, a hole for picking up intake manifold vacuum and a mounting hole for mounting an exhaust gas recirculation (EGR) pipe that feeds a part of exhaust gas discharged from the engine to the intake manifolds. In addition, there are known intake manifolds made of a resin material for the purpose of reduction of weight of vehicles. Japanese Patent Application First Publications Nos. 10-281025, 9-317579 and 9-68118 disclose such the intake manifolds.
It is generally known that a turbulent flow of the intake air flowing into the intake manifold is caused as the throttle valve opens and closes. The turbulent flow generates noise within the intake manifold, which is radiated from the intake manifold to surroundings.
In the Japanese Patent Application First Publication No. 10-281025, there is described a sound insulating wall provided on a curved outer peripheral surface of the intake manifold. However, the arrangement will undesirably limit an installation space around the intake manifold.
Further, in the intake manifold having the above-described holes positioned immediately downstream of the throttle body, a so-called whistling noise is occasionally caused upon the intake air flowing from the throttle body into the intake manifold.
Meanwhile, in the case of the intake manifold made of a resin material, it will be undesirably expected that high temperature of the exhaust gas recirculated to the intake manifold causes problems such as, for instance, thermal deformation, strength deterioration and the like.
In the Japanese Patent Application First Publication No. 9-68118, the EGR pipe includes a double-walled end portion projecting into the intake manifold. The end portion includes inner and outer pipes and radiating panels disposed on an outer surface of the outer pipe. However, the arrangement of the conventional technique is complicated and low in cost performance.
In the Japanese Patent Application First Publication No. 9-317579, the EGR pipe includes a main pipe and branch pipes diverged from the main pipe. Each branch pipe has an end portion curved toward the downstream side of the intake air flow in order to prevent the high temperature exhaust gas flowing therein from directly blowing onto an inner surface of the intake manifold. A mounting hole for the curved branch pipe is formed in a tapered recessed wall portion of the intake manifold. The tapered recess has a relatively large size in order to easily mount the curved end portion of the branch pipe to the intake manifold. When the air flows into the intake manifold, turbulence will be generated in the air in the intake manifold due to the tapered recess. This will cause noise and then noise radiated from the intake manifold.
It is an object of the present invention to provide an intake manifold and an air intake system for an internal combustion engine that are capable of eliminating the above-described disadvantages of the conventional techniques.
According to one aspect of the present invention, there is provided an intake manifold for allowing an air flow into an internal combustion engine, comprising:
a wall defining an intake bore through which the air flow passes, said wall including a mounting portion; and
a noise reducer reducing noise generated within the intake bore, said noise reducer including a base wall, which defines an aperture substantially aligned with the intake bore of the wall and has a mounting surface connected with the mounting portion of the wall, and a cover wall extending from the mounting surface into the intake bore toward the downstream side of the air flow and covering at least a portion of a circumferential inner surface of the wall.
According to a further aspect of the present invention, there is provided an air intake system for controlling a flow of air into an internal combustion engine, comprising:
a throttle body including a first wall defining a throttle bore into which the air flows and a throttle valve moveably disposed within the throttle bore, said first wall including a first mounting portion;
an intake manifold including a second wall defining an intake bore, said second wall including a second mounting portion; and
a noise reducer reducing noise generated within the intake bore upon the throttle valve moving, said noise reducer including a base wall that defines an aperture substantially aligned with the throttle bore of the throttle body and the intake bore of the intake manifold and includes a first mounting surface connected with the first mounting portion of the throttle body and a second mounting surface connected with the second mounting portion of the intake manifold, said noise reducer including a cover wall extending from the second mounting surface into the intake bore toward the downstream side of the air flow and covering at least a portion of a circumferential inner surface of the second wall.
According to a still further aspect of the present invention, there is provided An intake manifold for allowing air to flow into an internal combustion engine, comprising:
first wall means for defining an intake bore in which the air flows; and
second wall means for reducing noise generated within a portion of the intake bore, said second wall means covering at least a portion of a circumferential inner surface of the first wall means which surrounds the portion of the intake bore.